Hi Matwey, On Mon, 8 Jan 2018, Matwey V. Kornilov wrote: > 2018-01-08 19:32 GMT+03:00 Johannes Schindelin <Johannes.Schindelin@xxxxxx>: > > > > On Mon, 8 Jan 2018, Matwey V. Kornilov wrote: > > > >> 2018-01-08 17:42 GMT+03:00 Matwey V. Kornilov <matwey.kornilov@xxxxxxxxx>: > >> > 2018-01-08 16:56 GMT+03:00 Johannes Schindelin <Johannes.Schindelin@xxxxxx>: > >> >> Hi Matwey, > >> >> > >> >> On Mon, 8 Jan 2018, Matwey V. Kornilov wrote: > >> >> > >> >>> I think that rebase preserve-merges algorithm needs further > >> >>> improvements. Probably, you already know it. > >> >> > >> >> Yes. preserve-merges is a fundamentally flawed design. > >> >> > >> >> Please have a look here: > >> >> > >> >> https://github.com/git/git/pull/447 > >> >> > >> >> Since we are in a feature freeze in preparation for v2.16.0, I will > >> >> submit these patch series shortly after v2.16.0 is released. > >> >> > >> >>> As far as I understand the root cause of this that when new merge > >> >>> commit is created by rebase it is done simply by git merge > >> >>> $new_parents without taking into account any actual state of the > >> >>> initial merge commit. > >> >> > >> >> Indeed. preserve-merges does not allow commits to be reordered. (Actually, > >> >> it *does* allow it, but then fails to handle it correctly.) We even have > >> >> test cases that mark this as "known breakage". > >> >> > >> >> But really, I do not think it is worth trying to fix the broken design. > >> >> Better to go with the new recreate-merges. (I am biased, of course, > >> >> because I invented recreate-merges. But then, I also invented > >> >> preserve-merges, so ...) > >> > > >> > Well. I just checked --recreate-merges=no-rebase-cousins from the PR > >> > and found that it produces the same wrong result in my test example. > >> > The topology is reproduced correctly, but merge-commit content is > >> > broken. > >> > I did git rebase --recreate-merges=no-rebase-cousins --onto abc-0.1 v0.1 abc-0.2 > >> > >> Indeed, exactly as you still say in the documentation: "Merge conflict > >> resolutions or manual amendments to merge commits are not preserved." > >> My initial point is that they have to be preserved. Probably in > >> recreate-merges, if preserve-merges is discontinued. > > > > Ah, but that is consistent with how non-merge-preserving rebase works: the > > `pick` commands *also* do not record merge conflict resolution... > > > > I am sorry, didn't get it. When I do non-merge-preserving rebase > --interactive there is no way to `pick' merge-commit at all. Right, but you can `pick` commits and you can get merge conflicts. And you need to resolve those merge conflicts and those merge conflict resolutions are not preserved for future interactive rebases, unless you use `rerere` (in which case it also extends to `pick`ing merge commits in merge-preserving mode). Ciao, Johannes
